Various formats for photographic recording of digital soundtracks on motion picture film have been proposed. For example, U.S. Pat. No. 4,600,280, issued Jul. 15, 1986, describes a technique for recording a digital soundtrack on a film strip by exposing the film to modulated light from a light source. In one method disclosed in U.S. Pat. No. 4,600,280, an intermittent light beam (encoded with digital audio information) is scanned horizontally across the film, and the film is then advanced vertically and the scanning process repeated. U.S. Pat. No. 4,600,280 suggests alternatively that the light can be projected on the film through a linear array of solid state shutters or Bragg cell modulators.
U.S. Pat. No. 4,461,552, issued Jul. 24, 1984, also discloses a method in which digital audio is photographically recorded on motion picture film.
U.S. Pat. No. 5,453,802, issued Sep. 26, 1995, entitled "Method and Apparatus for Photographically Recording Digital Audio and a Medium having Photographically Recorded Digital Soundtracks" and assigned to Sony Electronics Inc., discloses a method and apparatus for photographically recording digital audio signals, and a medium having digital audio signals photographically recorded thereon. The text of U.S. application Ser. No. 07/896,412 issued as U.S. Pat. No. 5,453,802, is hereby incorporated into the present disclosure by reference.
U.S. Pat. No. 5,471,263, issued Nov. 28, 1995, entitled "Method for Recording a Digital Audio Signal on a Motion Picture Film" and assigned to Sony Corporation, also discloses a method for photographically recording digital audio signals on motion picture film, and a film having digital audio signals photographically recorded thereon.
Several formats for photographically recording digital data on film (in addition to an analog soundtrack) have been proposed.
For example, U.S. Pat. No. 5,327,182, issued Jul. 5, 1994 and assigned to Sony Electronics Inc., discloses motion picture film having analog audio signals photographically recorded in the area between the sprocket holes on one side (the "right" side) of the film and the film's picture area. Digital audio signals are also photographically recorded on the film in two areas: between the sprocket holes on the right side of the film and the analog audio signals; and between the sprocket holes on the left side of the film and the film's picture area.
For another example, PCT International Application WO 92/14239, by Dolby Laboratories Licensing Corporation, published Aug. 20, 1992 discloses motion picture film having digital audio signals photographically recorded in areas between the sprocket holes along one side (the "right" side) of the film, and analog audio signals photographically recorded in the area between the sprocket holes on the right side of the film and the film's picture area.
Typically, a soundtrack (digital or analog) is recorded on a "negative" film, and a theater-ready ("positive") print of color motion picture film is produced using this negative film and another negative film. The former negative film is produced by exposing film stock (typically "black and white" film stock) to optical signals (which represent digital or analog audio information). The latter negative film is color negative film which has negatives of the motion picture images recorded thereon. Both negative films are translated through a printer to photographically produce the theater-ready print (which has both positive images and audio information recorded thereon).
It would be desirable to use recording equipment of conventional optical design to photographically record digital data in multiple formats (as well as an analog soundtrack) in real time (e.g., at the conventional "real time" rate of 24 frames per second) on a "negative" motion picture film (for use in generating a positive print). However, the various available systems for photographically recording digital data on film in a single format are typically incompatible, in the sense that they employ light in different wavelength ranges to image the digital data on film.
For example, one digital soundtrack recording camera in commercial use (the Sony Model DFR-C2000A camera; available from Sony Corporation) employs red light from LEDs to record a digital soundtrack (in the "Sony SDDS" format to be discussed below) on conventional 35 mm "black and white" film stock which is very sensitive to red light but much less sensitive to green light (such as Eastman 2374 Single Layer Ortho-Chromatic Sound Negative Stock Film available from Eastman Kodak) to produce a sound negative film for use in producing a positive motion picture print. However, another one digital soundtrack recording camera in commercial use employs green light to record a digital soundtrack (in the Dolby "SR-D" format to be discussed below) on conventional 35 mm "black and white" film stock which is sensitive to green light but much less sensitive to red light (such as Eastman SO-213 Single Layer Ortho-Chromatic Sound Negative Stock Film available from Eastman Kodak).
Until the present invention, digital data (in multiple formats) had not both been recorded photographically on a single "black and white" motion picture film by sequentially illuminating the film with light of different wavelengths (two different wavelengths for two different formats). Nor had it been known how to photographically record digital data (such as soundtrack data) in each of two or more different formats, and also an analog soundtrack, in real time on a single motion picture film (or other photosensitive medium).